The present invention relates to a method of producing a magnetic head and, more particularly, to an improvement in an annealing method of a ferrite video head having a molded glass part. Still more particularly, the invention is concerned with a method which can simplify the known annealing treatment and which can avoid the bad influence of fluctuation of the treatment while ensuring its treatment effect.
Conventionally, for producing a video head of narrow track width, it is a common measure to form a head core having a width greater than the effective track width, notches being formed in both side portions of the head gap so as to define the desired track width, and these notches are filled with a glass mold, as will be described later with reference to the drawings. The head core thus formed is usually subjected to an annealing to relieve stress in the glass which remains as a residual stress as a result of cooling of the glass.
This annealing has been made under a condition which is the same as that of the annealing of the mold glass, by holding the core head at the annealing point of the glass for a suitable time and then gradually cooling the head core.
However, the anneal mechanism in this treatment, in which the annealing condition for the glass is directly applied to the ferrite-and-glass composite body used for such as magnetic head, has not been clarified yet.
The defect of this annealing treatment is that, since the annealing point is highly critical, the time required for relieving the residual stress in the glass is largely changed even by a small fluctuation of the temperature circa the given temperature.